Given the needs you listed, I would recommend hiring a design consultant who specializes in whole home audio. This is above what the average user deals with. If you are currently happy with the Sonos products, a Sonos ecosystem may meet your needs, but that would require Sonos units in each room/zone. That gives you some portability compared to in-ceiling / in-wall speakers. I don't have any personal experience with Sonos.
As to the home theatre, I would treat that system separately. You want a dedicated multi-channel receiver and speaker setup for proper home theatre. You might be able to tie in a wireless streamer to the receiver to connect to the rest of the house system, or install a couple of extra speakers if you want occasional ambient music in the theatre room that is connected to the house system. If you prewire the theatre, use conduit to run the cables inside to allow for expansion or changes later. Think about how many channels you will need and whether you will want ceiling speakers for ATMOS or Auro3D.
I use the Roon software in my home and it can do a lot of what you want. I have the Roon core on a PC that holds my music collection. You connect Roon end points (wirelessly or wired through your home network) to stream your music to. Roon also supports streaming services like Spotify, Tidal, Qobuz, etc. Through my phone and PC (or any other laptop or tablet that can install the Roon client software) I can control each end point (the core can play music as well). I can link end-points together and have them play the same music, and also have end-points play different music. There is independent volume control for each end-point.
The caveat is that each end-point is its own sound system. Endpoints can be different things. They can be complex and flexible like a laptop or Raspberry Pi minicomputer connected to an amplifier, or simple like one of many Roon ready network players like Bluesound powered streamers. The Roon software has an annual subscription or a life-time license.
If you go with a consultant, they can provide whole home audio systems where everything is integrated with touch screen panels in the home and additional control via cell phone apps. This would typically have a central location for your amplifiers and streamers as opposed to separate systems in each room. It's a very clean installation that hides the equipment away, but will cost significantly more than a DIY setup. For something of this scale you will benefit from the advice of a professional.